The present invention relates to an apparatus for shaping and cutting a thin thermoplastic sheet to make articles and for stacking the articles. The apparatus includes a heating element, a transporting element and a shaping station equipped with a movable table. The shaping station includes a combined shaping and cutting tool which, for the sake of simplicity, will be hereinafter referred to as the shaping tool. The lower portion of the shaping tool, which is mounted on the table, can be pivoted from a first position in which the shaping and cutting takes place, into a second position from which the stacking occurs. In that position, the articles are ejected into stacking troughs.
One problem in connection with a fast moving device which shapes and cuts articles made of a thin plastic sheet in one station is that the articles must be stacked when they are ejected from the mold nest. It is desirable to transfer the articles from the mold directly into stacking troughs, i.e. to not blow them out in an unordered fashion and then sort them again. U.S. Pat. No. 4,191,520 discloses that with with flat parts the transfer may be accomplished by discharging the articles and stacking them toward the top. This possibility, however, does not exist for larger articles which require the use of stretching aids. In this latter case, German Offenlegungsschrift (Laid-Open Patent Application) No. 2,517,981 discloses displacing the entire upper tool portion. This results in several problems relating to the number of articles transferred per unit time, heating, tightness and removal of the upwardly discharged and stacked articles.
Proposals have also been made to arrange a plurality of lower tool portions so that they rotate on a carrier and to then turn them, as for example described in U.S. Pat. No. 3,802,819. The major drawback here is that a plurality of shaping tools are required which is very expensive, particularly because these lower portions must all be exactly alike since they coact with the same matrix in the upper portion.
German Utility Model Pat. No. 70 15 773 discloses pivoting of the lower portion of a shaping tool toward the stacking station by 180.degree. after the shaping step. The drawback here is that the long path to be traversed by the shaping tool results in a low output of the device, and the energy requirement of the device is high. Moreover, the closing movement of the tool halves (for cutting) must here be effected by moving the upper portion of the shaping tool. Thus, two drives must be provided, namely one for the upper portion and one for the lower portion, and these drives must be accurately synchronized with one another's functions, which at the high output numbers required can be accomplished only in a positive mechanical way. Such a drive is complicated and expensive.
In the apparatus according to German Pat. No. 1,276,900, the lower portion of the shaping tool is pivoted about 90.degree.. The structural design of the apparatus does not permit a pivot angle of less than about 90.degree.. The drawback here is that the lifting movement for cutting is effected directly by way of a cam disc and therefore the cam roller must absorb the entire cutting force. The design of the apparatus does not permit the use of a bell crank drive. Another drawback is that the upper portion and the lower portion of the shaping tool cannot be guided relative to one another, for example, by means of guide column. The reason for this is that the lower portion performs only a pivoting movement and a very slight vertical lifting movement for cutting. The consequence of omitting such a guide is rapid wear of the cutting edges.